Data Supplement, Dunn et al., page 1

Data Supplement

The Sixth Mass (co)Extinction-Are Most Endangered Species Parasites and Mutualists?

Robert R. Dunn, Nyeema C. Harris, Robert K. Colwell, Lian Pin Koh, Navjot S. Sodhi

Supplement 1. Definitions of terms related to co-extinction.

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BOX: Definitions—The number of terms used to describe chains of extinction or co-extinctions has continued to grow through time. For example, while one body of literature has considered secondary extinctions at local scales, another literature has considered co-extinctions, typically at global scales. The two terms, however, are nearly or entirely synonymous. Here we offer brief definitions of the terms used in considering co-extinctions.

Co-extinction: Stork and Lyall (Stork & Lyal 1993) coined the term co-extinction to refer specifically to the extinction of host-specific parasites with the extinction of their hosts. The term has since been used more broadly to refer to the loss of one species as a result of the extinction of another species it depends on (e.g., Koh et al. 1994, Thacker et al. 2006).

Co-endangerment: Koh et al. (2004) coined the term co-endangerment to refer to the endangerment of an affiliate (parasite, commensal, or mutualist) due to the endangerment of the species on which it depends.

Secondary extinctions: This term refers to extinctions of species due to the extinctions of species on which they depend. It appears to be synonymous with the current use of co-extinction.

Trophic cascade: The term originally referred loosely to the consequences at one trophic level of a change in the composition of species at another trophic level (Paine 1980). Other authors (Pace 1999) prefer a more inclusive concept, referring to trophic cascades as "strong interactions within food webs that influence the properties of the system”—a definition broad enough to include some kinds of co-extinction.

Chains of extinction: Diamond (1989) appears to have introduced the term chains of extinction which, like co-extinction and secondary extinction, refers to additional extinctions that result from the extinction of some focal species. “Chains of extinction" however is broader in that it includes both co-extinctions and cases in which the loss of one species leads to increases in the abundance of other species and consequent ecological impacts.

Supplement 2. Carnivore parasite data.

We conducted a systematic literature review to compile a list of parasites for each of 29 terrestrial, North American species of the order Carnivora (Table 1). We searched peer-reviewed publications using several databases including the Global Mammal Parasites database, the Natural History Museum host-parasite database, and the Zoological Record. The keywords used in the search included the common name or scientific name of each species and of each (ecto) parasite or disease. We included studies published from January 1965 through May 2008 and inclusively defined parasites to cover microparasites (viruses, bacteria, and protozoa), macroparasites (helminthes) and ectoparasites (arthropods). Parasites reported from experimental manipulations or captive individuals were not included in the analysis.

Table 1

Common Name / Scientific Name
Family Canidae
Coyote / Canis latrans
Gray wolf / Canis lupus
Red wolf / Canis rufus
Gray fox / Urocyon cinereoargenteus
Island gray fox / Urocyon littoralis
Arctic fox / Vulpes lagopus
Kit fox / Vulpes macrotis
Swift fox / Vulpes velox
Red fox / Vulpes vulpes
Family Felidae
Canada lynx / Lynx canadensis
Bobcat / Lynx rufus
Cougar / Puma concolor
Family Mephitidae
Hog-nosed skunk / Conepatus leuconotus
Hooded skunk / Mephitis macroura
Striped skunk / Mephitis mephitis
Western spotted skunk / Spilogale gracilis
Eastern spotted skunk / Spilogale putorius
Family Mustelidae
Wolverine / Gulo gulo
American Marten / Martes americana
Fisher / Martes pennanti
Ermine / Mustela erminea
Long-tailed weasel / Mustela frenata
Black-footed ferret / Mustela nigripes
Least weasel / Mustela nivalis
American mink / Mustela vison
American badger / Taxidea taxus
Family Procyonidae
Raccoon / Procyon lotor
Family Ursidae
Black bear / Ursus americanus
Brown bear / Ursus arctos

Supplement 3. Estimates of the co-endangerment of plant parasites.

Plant parasites and co-extinction—The biggest determinant of the global magnitude of co-extinction rates has to do not with the parasites of vertebrates, but instead with the parasites, commensals and mutualists of tropical plants. By most estimates, tropical affiliates, and in particular parasitic or herbivorous insects, account for most species on Earth (Stork 1988). Yet there are still no consensus estimates of the average number of insect species found in a tropical tree, the average host specificity of those insects, or of the total number of tropical forest insect species on Earth (much less the rest of insect diversity). Perhaps the best studied region with regard to the diversity and host specificity of tropical herbivores is Papua New Guinea, where herbivores appear to be relatively generalist, with species feeding, on average, on 4.3 (butterflies)-6.8 (beetles) host species (Koh et al. 2004; Novotny et al. 2002). Hubbell et al. (2008) predicted that at least 20% of Amazonian trees are at risk of extinction due solely to forest clearance. Based on the assumptions that other plants and thus the tropical forests they comprise are at similar risk of extinction, and that there are roughly 310,000 plant species (Koh et al 2004), we used the nomographic model of Koh et al. (2004), to calculate the expected percentage of herbivores (saying nothing of mutualists, commensals or other sorts of parasites) that are co-endangered to be between 6.1% (beetles) and 9.4% (butterfly). Even if the diversity of herbivores is only two million species, this would mean that 123 to 188 thousand species of herbivores should be regarded as co-endangered. If, as some still argue, the diversity of tropical herbivores is closer to ten million species, these estimates increase fivefold—and so on for even higher estimates of herbivore diversity.

Supplemental Literature Cited

Diamond, J. M. 1989 Overview of recent extinctions. . In Conservation for the Twenty-first Century (ed. D. Western, Pearl, M.). Oxford: Oxford University Press.

Koh, L. P., Dunn, R. R., Sodhi, N. S., Colwell, R. K., Proctor, H. C. & Smith, V. S. 2004 Species coextinctions and the biodiversity crisis. Science305, 1632-1634.

Novotny, V., Basset, Y., Miller, S. E., Weiblen, G. D., Bremer, B., Cizek, L. & Drozd, P. 2002 Low host specificity of herbivorous insects in a tropical forest. Nature416, 841-844.

Pace, M. L. A. A. 1999 Trophic cascades revealed in diverse ecosystems. Trends in Ecology and Evolution14, 483-488.

Paine, R. T. 1980 Food Webs: Linkage, Interaction Strength and Community Infrstructure. Journal of Animal Ecology49, 667-685.

Stork, N. E. 1988 Insect diversity: facts, fiction and speculation. Biological Journal of the Linnean Society353, 321-337.

Stork, N. E. & Lyal, C. H. C. 1993 Extinction or Co-Extinction Rates. Nature366, 307-307.

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